1. Field of the Invention
The present invention relates to a stacked-layer film, a processing method of the stacked-layer film, semiconductor devices, and methods for manufacturing the semiconductor devices.
Note that in this specification, a semiconductor device refers to any device that can function by utilizing semiconductor characteristics, and an electro-optical device, a semiconductor circuit, an electronic device, and the like are all semiconductor devices.
In addition, the present invention relates to an object, a method, a method for producing an object, a process, a machine, manufacture, or a composition of matter. In particular, the present invention relates to, for example, a semiconductor device, a memory device, a display device, a liquid crystal display device, a light-emitting device, a driving method thereof, or a manufacturing method thereof. Alternatively, the present invention relates to, for example, an electronic device including the semiconductor device, the display device, or the light-emitting device.
2. Description of the Related Art
A technique for forming a transistor by using a semiconductor film formed over a substrate having an insulating surface has attracted attention. The transistor is applied to a wide range of semiconductor devices such as an integrated circuit and a display device. A silicon film and the like are widely known as a semiconductor film applicable to the transistor.
Whether an amorphous silicon film or a polycrystalline silicon film is used as a semiconductor film of a transistor depends on the purpose. For example, for a transistor in a large-sized display device, an amorphous silicon film is preferably used because a technique for forming a large-sized substrate has been established. On the other hand, for a transistor in a high-performance display device in which driver circuits are formed over one substrate, a polycrystalline silicon film is preferably used because the transistor can have high field-effect mobility. As a method for forming a polycrystalline silicon film, heat treatment at a high temperature or laser beam treatment which is performed on an amorphous silicon film has been known.
Furthermore, in recent years, an oxide-based semiconductor film has attracted attention. For example, a transistor which includes an amorphous oxide semiconductor film containing indium, gallium, and zinc and having a carrier density less than 1018/cm3 is disclosed (see Patent Document 1).
An oxide semiconductor film can be formed by a sputtering method, and thus can be used for a transistor in a large-sized display device. Since a transistor including an oxide semiconductor film has high field-effect mobility, the use of such a transistor can achieve a high-performance display device or integrated circuit in which driver circuits are formed over one substrate. In addition, there is an advantage that capital investment can be reduced because part of production equipment for a transistor including an amorphous silicon film can be retrofitted and utilized.
Further, in a transistor including an oxide semiconductor film, oxygen vacancies in the oxide semiconductor film may cause deterioration in electrical characteristics of the transistor. A technique of using an insulating film which releases oxygen by heating as a base insulating film and reducing oxygen vacancies in an oxide semiconductor film and an interface state between the base insulating film and the oxide semiconductor film by the oxygen released from the base insulating film is disclosed (see Patent Document 2).
Note that the size of transistors have steadily decreased by scaling law.